The present invention relates to an air-conditioning apparatus useful for temperature controlling of a machine tool, a measuring apparatus or an exposure apparatus for use in fabricating a semiconductor device, and also relates to a partition for use in the air-conditioning apparatus and an exposure apparatus equipped with the air-conditioning apparatus and the partition.
In the currently used ultra-high-precision machine tools and measuring apparatuses (e.g., an interferometer), very high working accuracy and measurement accuracy are often required. To meet the requirement of such very high accuracy, careful consideration must be taken to the entire arrangement and constitution of the apparatus, as well as the environment where the apparatus is placed. In particular, the change in temperature of the environment apparently affects the accuracy of the apparatus to a great extent. Accordingly, it is required to prevent the temperature variation in the environment to a minimum to achieve ultra-high-precision working accuracy and measurement accuracy. In general, a high accuracy of the apparatus can be achieved by placing and operating the apparatus in a constant temperature room where the room temperature is controlled. However, for an apparatus in which a still higher accuracy is required and therefore a precise temperature control in the environment when the apparatus is placed is needed, the accuracy can be achieved by providing a chamber for the apparatus and precisely controlling the temperature of the interior of the chamber by means of an air-conditioner installed outside of the chamber.
The schematic illustration of a conventional air-conditioning apparatus used for the temperature control of an ultra-high-precision machine tool or measuring apparatus is shown in FIG. 4. FIG. 4 illustrates an example of a reduction projection exposure apparatus for use in the manufacture of an integrated circuit (IC), which comprises the main body of the reduction projection exposure apparatus, a chamber and an air-conditioning apparatus. A light or laser beam 4 emitted from a light source 3 which is placed in a case different from the chamber, is irradiated onto a reticle 6 on which a circuit pattern for the integrated circuit is formed. The light or laser beam 4 passed through the reticle 6 is incident to a projection lens 5, where the light or laser beam is converged (e.g., converged to ⅕) and then irradiated onto a silicon wafer 7 mounted on a wafer stage 8. The silicon wafer 7 is mounted on the wafer stage 8 and is configured to be movable on a plane perpendicular to the light axis of the projection lens 5 by means of a movement mechanism for the wafer stage 8 in accordance with a command output from an external device. Upon the alignment of the wafer stage 8 being completed, the light or laser beam 4 emitted from the light source 3 is irradiated onto the reticle 6 and then converged through the projection lens 5 to project the circuit pattern formed on the reticle 6 onto a chip or shot region on the silicon wafer 7, whereby a photosensitive agent applied on the chip or shot region on the silicon wafer 7 is exposed to the light or laser beam 4.
Upon the reduction projection exposure process being completed, the wafer stage 8 is driven again to be aligned. Then, the subsequent reduction projection exposure process is performed. In this manner, with the repeated alignment and exposure process, the circuit pattern for the IC is projected in reduced form onto the silicon wafer 7.
The reduction projection exposure apparatus is subjected to the change in temperature of the environment and the vibrations transmitted to the apparatus, resulting in the formation of uneven line widths. For the purpose of eliminating these causative factors as much as possible, the main body of the reduction projection exposure apparatus is mounted on a vibration isolation table 2 and the entire apparatus is housed in a chamber 9. The chamber 9 receives air 12 brown from an air-conditioner 10 which comprises an air-blower 13 (which serves both as an air-blower and an air exhauster) and a heat exchanger 11. The temperature-controlled air is fed into the chamber 9 via a duct 15 and a filter 14. The temperature in the chamber 9 is continuously monitored by a sensor. The signal output from the sensor is fed back into the air-conditioner 10 to control the air-conditioner 10 so that there is no difference between the actual temperature in the chamber 9 and the set temperature. The chamber 9 has a partition having high thermal insulating properties so that the temperature variation occurring outside of the chamber 9 gives no influence on the temperature inside of the chamber 9. A conventionally used partition is one having a cross-sectional structure as shown in FIG. 5. The partition consists of a rigid urethane foam 17 sandwiched by a pair of steel or aluminum plates 16. The partition is used for imparting a strength to the chamber, and also used primarily in expectation of its thermal insulating effect.
The main body of the reduction exposure apparatus in the chamber 9 is mounted on the vibration isolation table 2 which is mounted on an independent base 21 on the ground 20. The chamber 9 and the air-conditioner 10 are mounted on a floor member 23 which is supported by struts 22 on the ground 20. A cushioning material 24 is filled between the floor member 23 and the independent base 21.
The recent demand for ultra-high-precision in an apparatus has been increased to a level that cannot be achieved merely by the temperature control of the environment around the apparatus.
For example, the line width of an IC pattern required in such a reduction projection exposure apparatus as mentioned above is less than 0.35 xcexcm. In the future, the reduction projection exposure apparatus would be expected to cover line widths around 0.25 xcexcm and even around 0.15 xcexcm. In this connection, even negligible disturbance factors that have been hitherto insignificant are increasingly becoming the topic, and the countermeasures against such disturbance factors should be taken.
What is consider as one of the disturbance factors is a noise transmitted to a chamber from the environment where the chamber is installed through a partition. In the case of a reduction projection exposure apparatus, a chamber typically is installed in a clean room. Noises generated in the clean room are transmitted to the partition of the chamber via air (as a medium), and transmitted in turn from the partition to the main body of the reduction projection exposure apparatus or the individual constituent parts (e.g., a projection lens, a stage and a wafer) to cause vibration thereof. As a result, there will be came up some problems, such as relative displacement among the individual constituent parts of the reduction projection exposure apparatus and difficulty in constantly maintaining a fine line width on the exposed plane.
The data of the noise levels measured both inside and outside of the chamber installed in a clean room is shown in FIG. 6. During the measurement, the air-conditioner which blows air into the chamber is stopped to detect only the noises intruding from the outside of the chamber. The partition of the chamber used is a conventional one having a cross-sectional constitution as shown in FIG. 5. As shown in the graphs of FIG. 6, even inside of the chamber, extremely low-frequency noises out of the audio range (i.e., low-frequency vibrations transmitted as compressional waves in air) are detected, which have sound pressure levels of about 69 dB at the maximum. It may suppose that the low-frequency noises are generated by a large air-blower for temperature-controlling the clean room and a duct which guides the temperature-controlled air into the chamber, and that the noises intruding into the clean room are transmitted to the chamber through the partition of the chamber. Comparing the noises with the date for the noise levels separately measured outside of the chamber, it can be found that, although the conventional partition exerts a satisfactory sound-proofing or noise-insulating effect against high-frequency noises having frequencies higher than about 60 Hz, it exerts less insulation effect on extremely low-frequency noises having frequencies of a few to several tens of Hz.
The influence of the noises in the interior of the chamber illustrated in FIG. 6 on the accuracy of the apparatus housed in the chamber is simulated taking the case where the main body of a reduction projection exposure apparatus is installed in the chamber. The results are shown below. The relationship between a sound pressure level (SPL) and a force per unit area generated by the sound pressure level is expressed by the following equation (1):
p=10xxc3x9710xe2x88x921 (Pa)xe2x80x83xe2x80x83(1)
wherein X=(S-74)/20;
P: a force acting on a unit area (Pa); and
S: a sound pressure level (dB).
The relation between a sound pressure level calculated in accordance with the equation (1) and an acceleration by vibration observed on a vibration isolation table 2 on which the main body of a reduction projection exposure apparatus is mounted, is shown in FIG. 7. The vibration isolation table 2 used is of an active-control type, and the calculation is made on the presumption that the vibration isolation table 2 has an attenuating ability of about xe2x88x9230 dB in a low frequency vibration range. From the noise measurement data shown in FIG. 6 and the calculated data shown in FIG. 7, it is considered that the acceleration by vibration observed on the vibration isolation table 2 on which the reduction projection exposure apparatus is mounted would be about 1 mgal at the maximum.
Under normal circumstances, a value xe2x80x9c1 mgalxe2x80x9d for the acceleration is considered to be very small which have little influence on the accuracy of an apparatus. However, in a reduction projection exposure apparatus by which micro-processing or micro-machining is to be performed, is of the significant meaning. Moreover, the acceleration of xe2x80x9c1 mgalxe2x80x9d is caused only by the noises in the chamber. In practice, vibrations transmitted from the ground 20 through an independent base 21 and so on are further added to the vibrations caused by the noises, which is a serious problem. Therefore, it is required to take some measures against this problem.
The air-conditioning apparatus according to the present invention includes a partition having a first plate member disposed on the side of an air-conditioned space which is conditioned by an air-conditioner and a second plate member disposed on the side of a space which is different from the air-conditioned space; the apparatus having a matrix material which is disposed between the first and second plate members; the matrix material comprising a plurality of cells each having a pair of side faces of a predetermined shape which face the first and second plate members, respectively.
The partition according to the present invention comprises a first plate member disposed on the side of an air-conditioned space and a second plate member disposed on the side of a space which is different from the air-conditioned space; the partition having a matrix material disposed between the first and second plate members; the matrix material comprising a plurality of cells each having a pair of side faces of a predetermined shape which face the first and second plate members, respectively.
The exposure apparatus according to the present invention comprises a main body of the exposure apparatus which transfers a pattern formed on an original plate onto a photosensitive substrate by exposure of light and a chamber which is provided around the main body to house the main body; the chamber having a first plate member which is disposed in the interior of the chamber, a second plate member which is disposed in the exterior of the chamber and a matrix material disposed between the first and second plate members; the matrix material comprising a plurality of cells each of which has a pair of side faces of a predetermined shape facing the first and second plate members, respectively, and which are disposed between the first and second plate members.
Each of the cells preferably comprises a hollow member having a pair of side faces of a predetermined shape, whereby weight of the cells can be reduced.
The matrix material preferably comprises a ceramic honeycomb structural material, whereby its rigidity is increased.
The air-conditioning apparatus according to the present invention comprises a chamber, a duct and an air-conditioner; the chamber having a partition which comprises a cellular material such as a honeycomb structural material.
The exposure apparatus having a chamber which houses the apparatus therein according to the present invention has a chamber partition which comprises a cellular material, such as a honeycomb structural material.
This specification includes part or all of the contents as disclosed in the specification and/or drawings of Japanese Application No. 10-15884, which is a document declaring a right of priority of the present application.